ON THE ANATOMT OF FISHES. 
143 
well as the structure of the triangular sheets of the dorsal wall and their mode of 
connection with the crescentic processes of the tripodes, are substantially the same as 
in Arius pidada and its allies, and this resemblance extends also to the condition of 
the Weberian ossicles. 
Lateral cutaneous areas {l.c.a.) are formed by the divergence of the dorso-lateral 
and ventro-lateral muscles of the trunk, but a considerable amount of fatty tissue 
separates them from actual contact with the adjacent lateral walls of the anterior 
chamber of the air-bladder. 
Osteogeniosus macrocephcdus and 0. militaris. 
These species require no special notice. In each case the air-bladder is almost 
identical in structure with that of the preceding species. 
Group : — Baoarixa. 
Bagarius Yarrellii. 
In Bagarius we again meet with an example of the effects of degeneration in 
retrogressively modifying the structure of the air-bladder. 
Cuvier and Valenciennes (8) denied the presence of an air-bladder in Bagarius, 
but as far back as 1831, Taylor (38) had previously affirmed its existence in the 
form of two small sacs having no communication with each other or with the 
alimentary canal, and so small that each sac in a Fish weighing ten pounds was not 
larger than an ordinary garden pea. By the same observer it was also stated that 
the two sacs were situated one on each side of the body in a deep groove or furrow 
formed by the consolidated transverse processes of the cervical vertebrse, at about an 
equal distance from the common integument and the vertebral column, and 
immediately behind the pectoral fin. Taylor’s account was subsequently confirmed 
by Day (9) in the following terms : — “ Air-vessel small, consisting of two rounded 
portions situated on either side of the bodies of the anterior vertebrse, and partially 
enclosed in bone.” 
In the structure of the air-bladder and the nature of the correlated skeletal 
modifications Bagarius bears a strong resemblance to Akysis and Acrochordonichthys, 
but more particularly perhaps to Glyptosternum, of which an account will subsequently 
be given. 
Mainly owing to the massive growth of the superficial ossifications the centra of 
the complex and fifth vertebrae are firmly anchylosed to each other, and to the skull 
(fig. 53). The centrum of the first vertebra is not only very small, but so completely 
is it enclosed within tlie contiguous concavities of the basioccipital and complex 
centrum, that no external indications of its existence can be detected. The centrum 
